A catastrophic earthquake in Southern California would almost certainly collapse bridges, destroy roads and render hundreds of hospital beds useless, while leaving tens of thousands in need of medical care.

With key medical health facilities out of commission, emergency responders say many of the injured would be treated in tents set up at field hospitals wherever needed.

"Each hospital has surge tents that have been prepositioned over the years," said Jerry Neverez, a registered nurse who coordinates hospital preparedness planning for Inland Counties Emergency Management Agency.

The tents are stored in emergency trailers with other provisions.

At each hospital, the trailers are packed with water, cots, decontamination showers, hazmat suits and other supplies, said Joey Hunter, St. Bernardine Medical Center's public safety director.

In addition, San Bernardino County has 36 field tents that would be immediately available for field treatment, Neverez said. Each tent is double-walled, built to military standards and has room for caregivers to treat 10 patients at a time.

A quake-stricken area would also have access to at least one of the state's three mobile hospitals - a series of huge tents, each large enough for 200 beds. The tents include emergency rooms, laboratories, intensive care units and up-to-date supplies. Stored at undisclosed sites around the state, they are designed to be deployed within 72 hours.

Besides tents, hospital administrators have "surge plans" to move patients to other facilities when a massive earthquake or other catastrophic event strikes.

A key test of St. Bernardine Medical Center's surge plan will come next month, when it moves students playing the roles of patients to nearby Waterman Convalescent Hospital. The drill will take place at the same time as a statewide test challenging hospitals to practice their response to a four-day loss of water.

Waterman Convalescent has 166 beds. If all San Bernardino County hospitals gain the ability to move patients to skilled nursing facilities, caregivers would have an additional 3,000 hospital beds to treat the injured, Hunter said.

After an earthquake, one of responders' first tasks will be to learn which hospitals can accept patients, and where the field hospitals will need to be established.

"In a disaster situation, that's not really something you can plan for in advance, because you don't know the damage to each hospital," Colton fire chief Tom Hendrix said.

Similarly, Redlands Fire Battalion Chief Scott MacDonald said available engine companies will be sent to roam the streets to assess damage to hospitals and other buildings.

"Nothing's really written yet, but we plan to do a field treatment hospital," said MacDonald, who is in charge of his department's disaster planning.

"It's something like a MASH unit type thing."

Field hospitals might be set up outside an inoperable hospital or in locations where transporting the injured was not an option.

San Bernardino County's Office of Emergency Services, part of the county fire department, is responsible for creating a mass care and sheltering plan to guide emergency officials' response to an earthquake or other calamity.

The report is not completed, but may be released in about two months.

If the reality of a major earthquake accords with current scenario planning, firefighters in Colton, Redlands and other Inland Empire cities will not be able to take patients to most nearby hospitals in the days after rupture.

In a 2008 USGS scenario, seismologists and first responders anticipated that a major earthquake would knock out 60 percent of the hospital beds in Los Angeles, San Bernardino, Riverside and Orange counties.

Writing the most comprehensive analysis of what "The Big One" might do to Southern California, experts predicted that in San Bernardino County alone, damage to four hospitals would render 1,479 hospital beds unavailable.

That accounted for 37 percent of San Bernardino County's licensed hospital beds.

But as comprehensive as the ShakeOut scenario is, Hawkins cautioned there is no way to predict everything that can go wrong.

For example, Japanese authorities devote extraordinary effort to earthquake preparation, but Hawkins said they did not anticipate a simultaneous seismic event and a nuclear crisis, which is exactly what happened at the Fukushima nuclear plant last March.

The USGS scenario does not take into account new Kaiser Permanente hospitals in Fontana and Ontario - the former expected to open in 2013, built to strict new seismic safety standards.